Carbon nanomaterials have garnered much interest due to their potential applications in bioimaging, photocatalysis, and light-emitting devices. Since 2006, carbon quantum dots (“CQDs”) have been utilized as fluorescent agents for biomedical applications, especially for in vitro and in vivo fluorescence bioimaging. In addition to their use as fluorescence imaging agents, CQDs have also found use as drug delivery agents by conjugating the CQD with active therapeutic drugs or biomolecules, such as doxorubicin (DOX), platinum-based drugs, aptamer, protein and so on, through surface functionalization for simultaneous imaging and therapeutic applications. For example, Huang et al. designed a novel theranostic platform based on carbon quantum dots conjugated with a photosensitizer. The conjugation of phytochlorin (“Ce6”) with a CQD can overcome some of the disadvantages of unmodified phytochlorin, such as prolonged cutaneous photosensitivity, poor water solubility and inadequate selectivity. The prepared CQD-Ce6 displayed enhanced photosensitizer fluorescence detection and remarkable photodynamic efficacy upon irradiation, which could act as a good candidate for simultaneous enhanced photosensitizer fluorescence detection (PFD) and photodynamic therapy (PDT) of gastric cancer tumor. Recently, Choi et al. developed a similar theranostic platform based on folic acid (FA) conjugated carbon dots loaded with zinc(II)-phthalocyanine to realize targeted delivery and photodynamic therapy.
However, the preparation of CQD-based drug delivery systems involves complex, multistep and time-consuming reactions, and inconvenient post-synthetic treatments. Thus, developing a simple and convenient way for the preparation of porphyrin-based carbon quantum dots remains highly desirable. In addition, the active targeted drug delivery and release technology has become a major area of research, as it can reduce systemic exposure to the drug and thus decrease the drug's side effects. These advantages are particularly important in the administration of therapeutics with harmful side effects, such as anti-cancer agents. Therefore, there is a need to develop new targeted delivery methods useful in the targeted treatment of diseases, such as cancer.